The present invention is another of a series of improvements stemming from an initial development by the assignee of this application, in the area of flat antennae. That initial development, disclosed and-claimed in U.S. Pat. No. 4,761,654, relates to a flat plate or printed circuit antenna in which all of the elements, including the ground plane, feedline, feeding patches, and radiating patches, are capacitively coupled to each other. The inventive structure enables either linear or circular polarization. A continuation-in-part of that application, application Ser. No. 06/930,187, now U.S. Pat. No. 5,005,019 discloses and claims slot-shaped elements. The disclosures of these patents are hereby incorporated herein by reference.
Previously, in such flat plate antennae, it has been known to provide input power to the array at a single feedpoint, and then to use a printed line, such as stripline, to carry power through a power divider network (PDN) to the various elements of the array. However, for large arrays, such as those which are perhaps one meter wide, using a printed distribution line results in unacceptably high losses. It would be desirable to minimize these losses.
Another copending, commonly assigned application, Ser. No. 07/210,433, discloses two improvements, including the incorporation of a low noise block (LNB) down-converter into the power divider structure, at a sacrifice of array elements. Another improvement disclosed therein is the use of coplanar waveguide technology to provide a power connection to the feedpoint of the array. The remainder of the feeding to the elements of the array is done in stripline, or another type of technology such as microstrip, finline, or slotline. The disclosure of that copending application also is incorporated herein by reference.
The limited use of the waveguide structure, and the resulting extensive use of etched power distribution lines in the antenna results in undesirably high loss.